It is necessary in the manufacture of yarns in certain work steps to separate the fibers to be processed from each other, that is, to open their composition with each other. It is necessary, for example, in other manufacturing steps, to align fibers as parallel to each other as possible. This procedure is called parallelization. The fibers to be processed enter into a mechanical contact with the processing devices during opening as well as during the parallelization of the fibers. As a consequence of the mechanical contact, a mechanical wear occurs on the devices that is, on the one hand, disadvantageous for the service life of the devices and, on the other hand, for the quality of the produced products. Such wear phenomena are especially noticeable in opening devices of open-end spinning machines wherein the opening rollers rotate at speeds of a few thousand rotations per minute. The projection or “cam” elements fastened on their circumference strike the fibers to be individualized at a high speed and accelerate them, while sharply abrasive forces act on the corresponding structural parts of the devices. One possibility of designing the cam elements consists in providing an opening roller with a plurality of needle elements that separate fibers, e.g., from a sliver at every rotation and entrain them. Another technical solution provides designing the cams in the form of a working surface with sawteeth. In this instance, clothing wires in particular have proven themselves that consist of a long metal wire from which the saw-toothed contour is stamped out. The wire produced in this manner is then fastened to the opening roller with a helical groove. Another solution provides designing the opening rollers in one piece. In this instance saw-toothed geometries are formed into a single-piece workpiece, e.g., by turning and grinding.
The surface of the cams must therefore be as resistant as possible on account of the high mechanical wear. Moreover, there is the requirement of manufacturing such wear parts as economically as possible and therewith keeping the assembly cost as low as possible. Thus, e.g., especially hard surface coatings or top structures are known; however, they can either not be worked or can only be worked with great difficulty. Furthermore, the surface properties placed on the materials to be worked must be adapted, as result of which the use of certain surfaces that are easier to work is partially excluded.